An aneurysm is an abnormal bulge or ballooning of the wall of a blood vessel. Typically, an aneurysm develops in a weakened wall of an arterial blood vessel. The force of the blood pressure against the weakened wall causes the wall to abnormally bulge or balloon outwardly. One detrimental effect of an aneurysm is that the aneurysm may apply undesired pressure to tissue surrounding the blood vessel. This pressure can be extremely problematic especially in the case of a cranial aneurysm where the aneurysm can apply pressure against sensitive brain tissue. Additionally, there is also the possibility that the aneurysm may rupture or burst leading to more serious medical complications including mortality.
When a patient is diagnosed with an unruptured aneurysm, the aneurysm is treated in an attempt to reduce or lessen the bulging and to prevent the aneurysm from rupturing. Unruptured aneurysms have traditionally been treated by what is commonly known in the art as “clipping.” Clipping requires an invasive surgical procedure wherein the surgeon makes incisions into the patient's body to access the blood vessel containing an aneurysm. Once the surgeon has accessed the aneurysm, a clip is placed around the neck of the aneurysm to block the flow of blood into the aneurysm and prevents the aneurysm from rupturing. While clipping may be an acceptable treatment for some aneurysms, there is a considerable amount of risk involved with employing the clipping procedure for treating certain types of cranial aneurysms because such procedures generally require open brain surgery and the location of the aneurysm can pose risks and may even prevent using this kind of procedure.
Intravascular catheter techniques have been used to treat cranial aneurysms, and are generally more desirable because such techniques do not require cranial or skull incisions, i.e., these techniques do not require open brain surgery. Typically, these techniques involve using a catheter to deliver an occlusion device (e.g., embolic coils) to a preselected location within the vasculature of a patient. For example, in the case of a cranial aneurysm, methods and procedures which are well known in the art are used for inserting and guiding the distal end of a delivery catheter into the vasculature of a patient to the site of the cranial aneurysm. A vascular occlusion device which is generally attached to the end of a delivery member is then traversed through to the delivery catheter until the occlusion is delivered into the aneurysm. The methods for delivering an occlusion device in a catheter are well known to those of skill in the art.
Once the occlusion device has been delivered to and deployed into the aneurysm, the blood within the aneurysm will generally clot in and around the occlusion device to form a thrombus. The thrombus that forms seals off the aneurysm so that blood from the surrounding vessels no longer flows into the aneurysm, this prevents further ballooning or rupture. The deployment procedure is repeated until the desired number of occlusion devices are deployed within the aneurysm. Typically, it is desired to deploy enough coils to obtain a packing density of about 20% or more, preferably about 35% and more if possible.
The most common vascular occlusion device is an embolic coil. Embolic coils are typically constructed from a metal wire which may be wound into a variety of shapes, including a helical shape. As explained above, a procedure may require using numerous embolic coils so that there is a large enough surface area for blood to clot thereto. Sometimes the embolic coil may be situated in such a way within an aneurysm that there are relatively considerable gaps between adjacent coils which can allow blood to freely flow into and within the aneurysm. The addition of extra coils into the aneurysm does not always solve this problem because deploying too many coils into the aneurysm may lead to an undesired rupture.
Another technique is to use meshes, similar to stents, to fill the aneurysm. The benefit to these devices is that they can expand many times the diameter needed to deliver the mesh through the catheter. This allows for a smaller length of mesh, in comparison to embolic coils, needed to achieve packing densities above 35%. The smaller length is dictated by the fact that the mesh can expand and thus occupy more space within the aneurysm even though it has a shorter length. By contrast, to achieve this same result, more (or longer lengths of) embolic coils are needed since they retain their diameter to fill the same void. FIG. 22 illustrates an example of a packing density comparison between a 1 mm outer diameter (OD) mesh, a 2 mm OD mesh and a 0.0150 inch (0.381 mm) OD embolic coil. In a 10 mm spherical aneurysm, an approximately 45% packing density is achieved with approximately a 7.5 cm length of the 2 mm mesh, an approximately 45% packing density is achieved with approximately 30 cm of 1 mm mesh and more than a 200 cm length of the embolic coil (at 0.015 in) is needed for an approximately 45% packing density.
This example highlights some of the challenges with mesh and embolic coils. For the mesh, there may not be sufficient length of the mesh in the aneurysm before density is reached. This leaves the mesh unsupported and can lead to compaction. Compaction is as it sounds, the mesh is compressed by blood flow into and past the aneurysm, and that decreases the portion of aneurysm treated by the mesh. Sometimes the portion treated is decreased below the point of being effective and a second procedure is needed to refill the aneurysm to get a sufficient packing density. For the embolic coil, they are typically much shorter than 200 cm and, as explained, multiple coils must be deployed into the aneurysm to reach an acceptable packing density, this increases the surgery time as each embolic coil must be advanced through the catheter.
Therefore, there remains for a better occlusion device that provides a greater occupied volume to promote the clotting of blood and decrease surgery time. The present invention presents such kinds of devices. Further, if multiple devices are used, the occlusion devices of the present invention can also effectively occupy the space between adjacent occlusion devices without increasing the risk of rupturing the aneurysm.